Various types of chassis sections used in Ladder frame construction

This is a discussion on Various types of chassis sections used in Ladder frame construction within 4x4 Technical, part of the 4x4 & Off-Roading category; @Sutripta 3 years back i was in college (so don't ask me to derive anything from the Torsion or Bending ...

@Sutripta 3 years back i was in college (so don't ask me to derive anything from the Torsion or Bending equation), also as i am a novice with very less offroading experience i leave it to the Jeep gurus to answer your queries on chassis flex.

Gentlemen, how exactly do you calculate torsional stiffness of a ladder-frame chassis? I know Finite Element Method simulation is the standard in the industry now, but lets say in terms of very basic written calculations for a very basic chassis design (ie. two box-section main rails of fixed dimensions, connected by 4 equally-spaced box section cross-members of same height all of same thickness).

If three parts of the frame are constrained at suspension mounting points (as was mentioned in this thread), and say an arbritary load of 1000kg (approx 9000N) is placed on the one unconstrained point of the frame - Is there any way to estimate the torsional stiffness by calculation rather than physical testing?

Also its pretty interesting to note that Mercedes uses tubular 'through frame' cross-members for they're G-wagen & Unimogs (check out the pics).

@ali khl the chassis splay in the above shown is constant throughout, you need not design a new cross member for each and every position, a closed tubular cross member would suffice, is the DAC of a load carrier?

@Sutripta 3 years back i was in college (so don't ask me to derive anything from the Torsion or Bending equation), also as i am a novice with very less offroading experience i leave it to the Jeep gurus to answer your queries on chassis flex.

Spike

PS-I have sent you a PM

Three years. Thats as fresh as they come. Now dust off your text books and calculator because you are now the official teaching assistant!

Replied to your PM.

Quote:

Originally Posted by ali_khl

Gentlemen, how exactly do you calculate torsional stiffness of a ladder-frame chassis? I know Finite Element Method simulation is the standard in the industry now, but lets say in terms of very basic written calculations for a very basic chassis design (ie. two box-section main rails of fixed dimensions, connected by 4 equally-spaced box section cross-members of same height all of same thickness).

If three parts of the frame are constrained at suspension mounting points (as was mentioned in this thread), and say an arbritary load of 1000kg (approx 9000N) is placed on the one unconstrained point of the frame - Is there any way to estimate the torsional stiffness by calculation rather than physical testing?

If the chassis is so simple that it almost the same as a wireframe, I suppose it could be solved analytically. Far more complex problems can be successfully predicted using FEA, as you have rightly said. So one can predict without building and testing an actual or a scale model. Whether I've answered your question, I don't know.

Quote:

Originally Posted by hgnishanth

OT: From your replies I guess you too are in the merchant navy?? Engineer??

Cheers

Nishanth

Me! No! Just the thought of sitting in the rear seat of a Scorpio makes me seasick! As landlubbery as they come.

In the Bolero Storm which sports the same suspension config i.e. Scorpio IFS upfront and Leaf Springs in the rear, there is no welding in betwen.
May be Spike can confirm this,

Bolero got Hydroformed chassis rails. So no issues for welding.

Quote:

Originally Posted by ex670c

The Front End of the Storm is from a 2WD Scorpio IFS Coil Springs
The Front End of the Thar is from a 4WD Scorpio IFS with Torsion Bar.

But the question still remains. If there is no joint in between, then how can a C in C Chassis is fitted/ combined with a Hydroformed BOX Chassis. (Pls forget about Scorpio IFS & Bolero names)

There has to be some method. I am asking this again & again coz Thar will be offered as an Offroader. Then will the chassis take all that pressure at the integration point? (A joint or Weld as marked in Orange)

Why this question is not answered with proper answer? :( I think this is also important.

If there is no joint in between, then how can a C in C Chassis is fitted/ combined with a Hydroformed BOX Chassis.
(Pls forget about Scorpio IFS & Bolero names)

There has to be some method. I am asking this again & again coz Thar will be offered as an Offroader. Then will the chassis take all that pressure at the integration point? (A joint or Weld as marked in Orange)
M&M .. RTI

@Offroad_maniac, hmm interesting question, it shows your eagerness to learn new things, i request the gurus to take over.

Spike

OT- can someone tell me who has told "the chassis is welded in between scorpio and bolero rails"

But the question still remains. If there is no joint in between, then how can a C in C Chassis is fitted/ combined with a Hydroformed BOX Chassis.

Sir,

Please explain what is a C in C chassis and what is a Hydroformed chassis?

The only two types of Chassis that I know are

Box Type Chassis

C-Channel Chassis.

Bolero is a box type chassis. Being from an automotive background and having seen chassis manufacturing up close, day in day out, I can tell you that it is one of the easiest processes compared to say panel welding et al.

I 'm definitely sure no manufacturer will be foolish enough to weld/join two different chassis as it is a definite recipe for disaster.

Please explain what is a C in C chassis and what is a Hydroformed chassis?

The only two types of Chassis that I know are

Box Type Chassis

C-Channel Chassis.

Bolero is a box type chassis. Being from an automotive background and having seen chassis manufacturing up close, day in day out, I can tell you that it is one of the easiest processes compared to say panel welding et al.

Hi MC... I am no sir. just a Comp guy.

For more details regarding C in C Construcion, refer to Post # 16 & #31 here. In short it is also a box section chassis formed by clubbing two C section long rails together. Eg. Scorpio Chassis.

Hydroformed Box means it is a single rectangular tubing throughout. There will be just one seamless weld as marked by red arrow (PIC 1).
Eg: Bolero & Army NGCS

Quote:

I 'm definitely sure no manufacturer will be foolish enough to weld/join two different chassis as it is a definite recipe for disaster.

Thats why I want some proper confirmation. Just Compare the pictures of Thar Front End Chassis with Back.

...If there is no joint in between, then how can a C in C Chassis is fitted/ combined with a Hydroformed BOX Chassis.

There has to be some method. I am asking this again & again coz Thar will be offered as an Offroader. Then will the chassis take all that pressure at the integration point? (A joint or Weld as marked in Orange)

M&M .. RTI

Hi,
Never seen the Thar in the flesh, let alone eyeballed its underpinnings, but I'm pretty sure its not a cut and shut job. The front and rear might be based on, similar to, inspired by etc. rather than is exactly the same as. That is assuming the rumours/ received wisdom is true. Leaving aside other technical issues, cut and shut would be an extremely unproductive and expensive means of manufacture.

Hi,
Never seen the Thar in the flesh, let alone eyeballed its underpinnings, but I'm pretty sure its not a cut and shut job. The front and rear might be based on, similar to, inspired by etc. rather than is exactly the same as. That is assuming the rumours/ received wisdom is true. Leaving aside other technical issues, cut and shut would be an extremely unproductive and expensive means of manufacture.

Could those in the know shed some light please.

Sutripta

I am also not quite sure. Guess it will remain as a puzzle which will be revealed as an engineering marvel after the launch.

would've been great if something is shared here (Not too technical but some small idea), as I think this kind of setup is very Unique & NEVER tried on any other manufacturers Box ladder frame.
(Guess M&M should have a patent then)

would've been great if something is shared here (Not too technical but some small idea),
Nevermind....

Sutripta, Ravi, welding is one of the operations involved while making a chassis, the members are cut to various lengths, blanked, pierced, bent to various shapes and then finally welded according to the requirements,

Sutripta, Ravi, welding is one of the operations involved while making a chassis, the members are cut to various lengths, blanked, pierced, bent to various shapes and then finally welded according to the requirements,

Sutripta, Ravi, welding is one of the operations involved while making a chassis, the members are cut to various lengths, blanked, pierced, bent to various shapes and then finally welded according to the requirements,